1. Field of the Invention
The present invention relates to an improvement on a metal terminal receptacle with stoppers for protecting its elastic tongue.
2. Description of the Related Art
FIGS. 4 and 5 respectively show a plan view and a front view of a conventional metal terminal receptacle with stoppers for protecting an included elastic tongue. The metal terminal receptacle A is formed by bending a plate, and an insertion portion A1 is formed at the left side of a base plate 1; a wire connecting portion A2 is formed at the right side.
In order to shape the insertion portion A1, the base plate 1 is bent at an end thereof to form a side wall 2, and the side wall is bent to provide an upper wall 3. Then, the upper wall 3 is further inwardly bent to form another side wall 2. As a result, the base plate 1, the side walls 2 and the upper wall 3 constitute a square case, as clearly illustrated in FIG. 7 which is a left side view of the metal terminal receptacle shown in FIG. 4.
An elastic tongue 4 is bent at an end of one of the side walls 2 and extends therefrom. As illustrated in FIG. 6, the elastic tongue 4 is further folded and is in press-contact with the other wall 12 by its resilience, and a supporting portion is formed between the elastic tongue 4 and the wall 2, where a male terminal is inserted and pinched.
Projections 5 as stoppers for limiting the deflection of the elastic tongue 4 within the elastic limit are provided on the base plate 1 and the upper wall 3. The projections 5 are formed by inwardly punching the plate 1 and the wall 3, for instance, through a press and by bending the punched portion upright. Both ends of the elastic tongue 4 abut the projections 5 to prevent the elastic tongue 4 from deflecting excessively beyond the elastic limit.
In order to decrease the resiliency at the tip of the elastic tongue 4, the width thereof is gradually reduced and a long hole 6 is provided. The wire connecting portion A2 on the right side of the base plate 1 is provided with two supporting portions 7 and 8, respectively, for a wire insulation portion and a conductor wire. However, the construction of the conventional metal terminal receptacle has the following problems.
In the manufacturing process of the metal terminal receptacle A, a punching work portion 10 is attached to an upper face of a lower metal mold 9 of the press, and the side faces of the punching work portion 10 are edged except for an inner side wall 10a to form the projections 5 on the base plate 1 and the upper wall 3. Then, the base plate 1 or the upper wall 3 is placed over the lower metal mold 9 as illustrated in FIG. 8A, and then, the upper metal mold 11 descends. As a result, a U-shaped cutout is formed on the base plate 1 and an upper wall 3, and then, a portion enclosed by the U-shaped cutout is inwardly bent so as to be upright to the base plate 1 or the upper wall 3 to form the projection 5 as indicated in FIG. 8B.
There are the following problems when the punching work is carried out. Firstly, burrs are brought about when the U-shaped cutout is formed, and the burrs cause the position of stoppers for limiting the deflection of the elastic tongue 4 to fluctuate. As a result, the elastic tongue 4 may abut the projections 5 even though the elastic deflection is not sufficient, or the elastic deflection of the elastic tongue 4 may become too large. Secondly, the height L of the projection 5 should be more than 1.5 times the plate thickness T to carry out the punching work, which considerably increases the height L of the projection 5. Therefore, as illustrated in FIG. 9, when the elastic tongue 4 is bent under the condition that the insertion portion 4 is being processed, a forming tool 12 for the elastic tongue 4 is interrupted by the projections 5, which makes the manufacturing work of the insertion portion A1 ineffective. Thirdly, the punching work portion 10 should be enlarged to improve the durability of the lower metal mold 9. However, openings 13 made by the punching work become large, resulting in decreased strength of the base plate 1 or the upper wall 3. Further, there is a unfavorable possibility that foreign materials enter the metal terminal receptacle A.